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Preparation of Gold?Tellurium Hybrid Nanomaterials for Surface-Enhanced Raman Spectroscopy
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Facile Synthesis of Catalytically Active Platinum Nanosponges, Nanonetworks, and Nanodendrites
No full textDetection of human serum albumin through surface-enhanced Raman scattering using gold "pearl necklace'' nanomaterials as substrates
No full textSynthesis and Applications of Tellurium Nanowires
No full text本篇論文的主要目的為發展簡易的方法來操控奈米材料的結構，包含碲（奈米線）、金-碲（奈米火材棒、奈米啞鈴及奈米豌豆）、金（奈米珍珠項鍊）及鉑（奈米海綿、奈米網及奈米軸突）。在這些奈米材料中，金屬組成是由金屬離子（AuCl43–和PtCl62–）與碲奈米線進行氧化還原反應所產生。論文共分五章，第一章介紹了奈米材料的物理和化學性質，同時也簡述了與論文相關之實驗技術及發展背景。第二章為開發室溫下合成螢光碲奈米線方法，此奈米線的合成主要是在高濃度的聯胺（N2H4）溶液中還原二氧化碲，經由碲離子（Te2-）的氧化及非結晶態碲奈米粒子的溶解產生碲原子來沉積在結晶態為三方晶形的碲奈米粒子上，操控碲奈米線成長的時間（40至120分鐘），可得到不同大小的碲奈米線，其長度範圍可從251 nm到879 nm，而寬度只由8 nm變化到19 nm。在第三章中，碲奈米線可進一步製備為三種具表面增強拉曼散射（surface-enhanced Raman scattering）效果的金-碲奈米基材（substrate）。在這個實驗中，碲奈米線除了作為金奈米粒子沉積的模板（template）外，也具有作為金奈米粒子還原劑的功能，在溴化十六碳烷基三甲銨（CTAB）為10 mM的條件下，操控碲奈米線與金離子反應的時間為10分鐘、20分鐘及60分鐘，可分別得到金-碲奈米啞鈴、金-碲奈米豌豆及金奈米珍珠項鍊等奈米材料；而在這些材料中，金奈米粒子在同一條碲奈米線中的距離也有所不同，可用來觀察其在表面增強拉曼應用上效果的差異。結果發現金奈米珍珠項鍊的增強效果最好，其增強效果可達5.6 x 109，且具再現性，推測是因其金奈米粒子間的距離較短，而造成較強的電磁場效應。在第四章中，金離子與碲奈米線的氧化還原電位會因不同的pH值而改變，故可藉之操控金奈米粒子的成核及成長速率，在10 mM的CTAB存在下，pH值為4及5時，分別可得到碲奈米線一端與兩端長金奈米粒子的產物。由光電測量的數據顯示金奈米粒子沉積的程度會改變碲奈米線所組成薄膜（film）的電阻，這也暗示這些所合成的金-碲奈米線有極大的潛力未來可被應用在電子元件上。最後一章介紹在水溶液中利用鉑離子與碲奈米線的氧化還原反應來合成孔洞性鉑奈米材料。藉由不同的溫度及十二烷基硫酸鈉（SDS）濃度等條件，可合成鉑奈米海綿、鉑奈米網及鉑奈米軸突等產物。首先在室溫下，鉑奈米海綿及鉑奈米軸突分別產生在較低（<10 mM）及較高（>50 mM）的界面活性劑條件下。而在溫度升高的情況下，鉑奈米網狀物及鉑奈米軸突可在較低（<10 mM）及較高（>50 mM）的界面活性劑條件下產生。經由穿透式電子顯微鏡的觀察，發現這三種奈米材料皆是由寬度為3 nm，長度為17 nm的一維鉑奈米結構所組成。循環伏安法（CV）所測得的數據顯示製備出來的鉑奈米海綿、鉑奈米網及鉑奈米軸突皆具有高的電化學活性表面積（77.0、70.4及41.4 m2 g–1）。至於在電催化甲醇氧化的部份，發現在鉑奈米海綿、鉑奈米網及鉑奈米軸突中，正向峰電流（If）與反向峰電流（Ib）的比值皆高（If/Ib = 2.88、2.66及2.16）。這表示這三種奈米材料在電催化甲醇氧化的部份，存在比傳統鉑奈米材料更佳的電催化活性及毒害容忍度。由於製備這些鉑奈米材料的方法較為經濟，且產物的純度極高，在穩定性及電催化活性上更有不錯的表現，相信有極大的潛力可被應用在燃料電池的催化劑上。This thesis focuses on developing facile synthetic approaches to fabricate nanomaterials of different compositions, including tellurium (nanowires), gold-tellurium (nanomatches, nanodumbbells, and nanopeapods), gold (pearl-necklace nanomaterials), and platinum (nanosponges, nanonetworks, and nanodendrites). These nanomaterials were prepared through galvanic replacement reactions between Te nanowires and metal ions (AuCl43– and PtCl62–). Chapter 1 introduces the physical and chemical properties of nanomaterials as well as briefly describes the techniques and background relating to this thesis. The development of synthesizing fluorescent Te nanowires at room temperature is discussed in chapter 2. The nanowires are prepared from the reduction of tellurium dioxide with concentrated hydrazine solution through deposition of Te atoms that are oxidized from telluride ions and dissolved from amorphous Te nanoparticles onto trigonal nanocrystallines. By carefully controlling the growth time from 40 to 120 min, different sizes of trigonal Te nanowires can be prepared; the length changes from 251 to 879 nm while the diameter only grows from 8 to 19 nm. In chapter 3, a simple method for preparing three different surface-enhanced Raman scattering (SERS)-active substrates is described. The as-prepared Te nanowires are used as templates and reducing agents for the deposition of Au nanoparticles. Through the reaction of Te nanowires with AuCl43– ions in the presence of hexadecyltrimethylammonium bromide (CTAB) over reaction times of 10, 20, and 60 min, Au-Te nanodumbbells, Au-Te nanopeapods, and Au pearl-necklace nanomaterials are obtained, respectively. By altering the reaction time, the distance between adjacent Au nanoparticles in each Te nanowire is tunable and allows investigating its effect on the SERS signals. Having shorter distances among Au nanoparticles (greater electromagnetic fields), the Au pearl-necklace nanomaterials provided a reproducible enhancement factor of 5.6 x 109. In chapter 4, an advanced approach for highly selective growth of Au nanoparticles onto Te nanowires is discussed. By carefully selecting the pH values to vary the redox reaction potential between AuCl43– ions and Te nanowires, allowing control of nucleation and growth rates of Au nanoparticles. In the presence of 10 mM CTAB, Au-Te (one end) and Au-Te-Au (both ends) nanowires are obtained at pH 4.0 and 5.0, respectively. Photovoltaic data revealed that the resistance of the Te nanowires-based thin film is controlled by the degree of deposition of Au nanoparticles. It is suspected that Au-Te and/or Au-Te-Au nanowires hold great potential for use in the fabrication of electronic devices. Chapter 5 describes synthesis of various porous Pt nanomaterials in aqueous solution through a similar chemical route. Employing different temperatures and concentrations of sodium dodecyl sulfate (SDS), Pt nanosponges, Pt nanonetworks, and Pt nanodendrites are obtained from the reduction of PtCl62– ions via galvanic replacement reactions with Te nanowires. At ambient temperature, Pt nanosponges and Pt nanodendrites formed selectively in the presence of SDS at concentrations of <10 mM and >50 mM, respectively. At elevated reaction temperatures, Pt nanonetworks and Pt nanodendrites were obtained in the presence of SDS at concentrations of <10 mM and >50 mM, respectively. TEM images revealed that these Pt nanomaterials are all composed of one dimensional Pt nanostructures having widths of 3 nm and lengths of 17 nm. Cyclic voltammetry data indicates that the as-prepared Pt nanonetworks, nanosponges, and nanodendrites possess large electrochemically active surface areas (77.0, 70.4, and 41.4 m2 g–1, respectively). For the electrocatalytic oxidation of methanol, the ratio of the forward oxidation peak current (If) to the backward peak current (Ib) of the Pt nanodendrites, nanosponges, and nanonetworks are all high (If/Ib = 2.88, 2.66, and 2.16, respectively). These three nanomaterials exhibit greater electrocatalytic activities and excellent tolerance toward poisoning species for the oxidation of methanol when comparing with the performance of standard Pt nanomaterials. Because of their low cost of preparation, high purity, good stability, and excellent electrocatalytic activities, it is believed that these as-prepared Pt nanomaterials will be effective catalysts for use in fuel cells.中文摘要 I鍵詞 IIbstract IIIeywords Vontents VIigure Contents IXonclusions and Prospects 101ublications 103onferences 106 Introduction 1.1 Nanomaterials 2.2 Characteristics of Nanomaterials 3.2.1 Surface Plasmon Resonance 3.2.2 Quantum Confinement Effect 5.3 Surface-Enhanced Raman Scattering 6.3.1 History 6.3.2 Enhancement Mechanisms 8.3.3 Single Molecule Detection 9.3.4 Designed Nanostructures 11.4 Direct Methanol Fuel Cells 12.4.1 Basic Concepts 12.4.2 Anode Catalysts 13.4.3 Cathode Catalysts 15.5 Motive of Research 16.6 References 18 Preparation of Fluorescent Tellurium Nanowires at Room Temperature 25.1 Introduction 26.2 Experimental Section 27.2.1 Chemicals 27.2.2 Synthesis of Tellurium Colloids and Nanowires 28.2.3 Characterization 28.3 Results and Discussion 29.3.1 Growth Mechanism 29.3.2 Length Control of Tellurium Nanowires 30.3.3 Optical Properties of Tellurium Nanowires 31.4 Conclusions 32.5 References 34 Preparation of Gold-Tellurium Hybrid Nanomaterials for Surface-Enhanced Raman Spectroscopy 44.1 Introduction 45.2 Experimental Section 45.2.1 Chemicals 45.2.2 Synthesis of Tellurium Nanowires 46.2.3 Preparation of Gold-Tellurium Nanomaterials 46.2.4 Preparation of SERS Samples 46.2.5 Characterization 47.2.6 Calculation of Enhancement Factor 47.3 Results and Discussion 47.3.1 Optical Properties of Gold-Tellurium Nanomaterials 48.3.2 Position- and Number-Controlled Growth of Gold Nanoparticles 48.3.3 SERS Measurements 49.4 Conclusions 51.5 References 52 Selective Growth of Gold Nanoparticles onto Tellurium Nanowires via a Green Chemical Route 59.1 Introduction 60.2 Experimental Section 61.2.1 Chemicals 61.2.2 Synthesis of Tellurium Nanowires 61.2.3 Selective Growth of Gold Nanoparticles 62.2.4 Preparation of Samples for Photovoltaic Measurements 62.2.5 Characterization 62.3 Results and Discussion 63.3.1 Growth Mechanism 63.3.2 Size Effects of Tellurium Nanowires and Gold Nanoparticles 64.3.3 Effects of pH and CTAB Concentration 64.3.4 Photovoltaic Measurements 66.4 Conclusions 67.5 References 68 Facile Synthesis of Catalytically Active Platinum Nanosponges, Nanonetworks, and Nanodendrites 76.1 Introduction 77.2 Experimental Section 78.2.1 Chemicals 78.2.2 Synthesis of Tellurium Nanowires 79.2.3 Preparation of Platinum Nanomaterials 79.2.4 Characterization 80.2.5 Electrode Modification 80.3 Results and Discussion 81.3.1 Growth Process and Formation Mechanisms of Platinum Nanosponges 81.3.2 Impact of Tellurium Nanowire and Hexachloroplatinate Ion Concentration 82.3.3 Impact of SDS and Reaction Temperature 83.3.4 Electrocatalytic Analysis 86.4 Conclusions 88.5 References 9
Direct methanol fuel cells using Se/Ru core/shell cathodes provide high catalytic activity and stability
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Detection of mercury(II) based on Hg2+–DNA complexes inducing the aggregation of gold nanoparticles
No full textSynthesis of Fluorescent Carbohydrate-Protected Au Nanodots for Detection of Concanavalin A and Escherichia coli
No full textDetection of aminothiols through surface-assisted laser desorption/ionization mass spectrometry using mixed gold nanoparticles
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